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204                     CONDYLARTHRA----PROTOGONIA                    CHAF
Creodonta. It has, as in Phenacodus, no orbital ring. Thu
fa.uin.erus resembles that of a Carnivore rather than that of ar
Ungulate. The carpus and tarsus are serial. The fibula articu-
lates with both the calcaneum and the astragalus, which is not
the case with Phenacodus. It is suggested that these animals
are ancestral forms of the Chalicotheres. In the brain the
hemispheres do not cover the cerebellum,
More primitive apparently than Phenacodus was the less-known
genus Suprotogonia> or Protogonia l as it has been called. The best-
known species is 18. puercensis, so called from its occurrence in the
Puerco beds of the American Eocene. It was a slender, long-
limbed creature, smaller than Phenacodus, with a long and heavy
tail as in that animal. Lake Phenacodus it was semiplantigrade,
and shows more likenesses to the Creodonta. The skull is only
known by a part of the lower jaw with teeth, and by the teeth of the
upper jaw. The vertebrae are not entirely preserved, but enough
remain to show that the animal had a tail of 16 or 17 inches, which is
a considerable length when compared to its height, about a foot at
the rump. In the fore-limb the most noteworthy point is that the
ulna has a convex posterior border as in the Creodonts, the same
border in Phenacodus being concave. The humerus is slender, with
less-marked tuberosities. The fifth digit seems to have been less
reduced. The phalanges seem to have borne horny sheaths some-
what intermediate between hoofs and claws. The pelvis is
described as being, as is also thab of Phenacodus, rather like that of
the Creodonta. The right hind-limb is known in all its details.
It appears that the bones are not serial but interlocking; this,
however, on the views with regard to the relations of these two
forms of tarsus mentioned on p. 198, does not militate against
regarding Euprotogonia, as the ancestor of the genus Phenacodus.
 The third toe is the pre-eminent one, the animal thus being
Perissodactyle. The lateral digits are larger than in Phenacodus,
and the metatarsals and the phalanges are slightly curved, which
is again a Creodont character as compared to the perfectly straight
corresponding bones of Phenacodus. It seems evident that this
animal is to be looked upon as a more ancient type than Phena-
codu$f even if not as its actual ancestor.
Another    group    of    the    Condylarthra   contains   'the    genus
Pertipychus and some others.     Periptychus has the full dentition
1 See W. D. Matthew, Bull. Afrvcr. Mus. Nat. Hist. ix. 1897, p. 303.